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采用超音速微粒轰击(SFPB)技术对铝合金2A14进行表面纳米化处理,利用X-射线衍射仪和透射电镜等研究材料表层的组织变化机理。结果表明:材料表面经强烈塑性变形形成30μm厚的纳米层,平均晶粒大小约为30 nm,平均微观应变为0.1294%。观察发现距表面200μm处的应变层存在纳米级位错胞,通过理论分析提出铝合金表面纳米晶层新的形成机理,原始粗晶被快速地一次分割成纳米级位错胞或层状胞块组织,随着胞壁柏氏矢量不断积累,晶粒的取向差不断增大形成纳米级亚晶,通过晶界滑移或晶体转动形成均匀、等轴、随机的纳米晶粒。
The surface nanocrystallization of aluminum alloy 2A14 was carried out by SFPB technique. The microstructure of the surface of the alloy was studied by X-ray diffraction and transmission electron microscopy. The results show that the surface of the material is strongly plastically deformed to form a 30μm-thick nano-layer with an average grain size of about 30 nm and an average micro-strain of 0.1294%. It is found that nanoclassical dislocation cells exist in the strain layer at a depth of 200 μm from the surface. A new formation mechanism of the nanocrystalline layer on the surface of the aluminum alloy is proposed through theoretical analysis. The original coarse crystal is rapidly segmented into nanometer-level dislocation cells or layered cell masses With the continuous accumulation of Berger’s vector in cell wall, the orientation difference of the grains increases to form nano-scale subgrains, which form uniform, equiaxed and random nanocrystalline grains through grain boundary slip or crystal rotation.